Pivoted inertia switch self-orienting along a line of deceleration in a prescribed angular pattern

ABSTRACT

An inertia switch assembly includes a support in the form of a casing in which an inertia switch body is mounted for free swinging in an angular pattern so that the switch body aligns itself with the direction of an applied force. Inertia means in the switch body responds slower to the applied force than the switch body. The inertia means include a conductive member which contacts terminal pins pivotally supporting the switch body.

United States Patent Miller [54] PIVOTED INERTIA SWITCH SELF- ORIENTINGALONG A LINE OF DECELERATION IN A PRESCRIBED ANGULAR PATTERN [72]inventor:

[73] Assignee:

James R. Miller, Huntington, N.Y.

Aerodyne Controls Corporation, Farmingdale, N.Y.

[22] Filed: Dec.8, 1970 [21] Appl.No.: 96,108

[52] U.S. Cl. [51] Int. Cl. [58] Field of Search ..200/6l.45-61.53;

[56] References Cited UNITED STATES PATENTS 2,972,134 2/1961 McKay..200/61.45 X

[is] 3,654,410 [451 Apr. 4, 1972 3,571,538 3/1971 Swanson ..200/61.47

3,049,700 8/1962 Du Plooy ..340/261 2,974,529 3/1961 Brueggeman et al...200/61.53 X

FOREIGN PATENTS OR APPLlCATlONS 386,034 1/1933 Great Britain ..340/262Primary Examiner-Robert K. Schaefer Assistant Examiner-M. GinsburgAttorney-Edward H. Loveman [57] ABSTRACT An inertia switch assemblyincludes a support in the form of a casing in which an inertia switchbody is mounted for free swinging in an angular pattern so that theswitch body aligns itself with the direction of an applied force.lnertia means in the switch body responds slower to the applied forcethan the switch body. The inertia means include a conductive memberwhich contacts terminal pins pivotally supporting the switch body.

10 Claims, 6 Drawing Figures PATENTEUAPR 41972 SHEET 1 0F 3 INVENTOR..JAMES R. MILLER FIG.5

ATTORNEY" PATENTEDAPR 4 4972 SHEET 2 UF 3 INVENTOR. JAMES R. MILLERATTORNEY PATENTEU PR 41912 SHEET 3 OF 3 INVENTOR. JAMES R. MILLERATTORNEY PIVOTED INERTIA SWITCH SELF-ORIENTING ALONG A LINE OFDECELERATION IN A PRESCRIBED ANGULAR PATTERN This invention concerns aswitch for triggering instant operation of a safety device when avehicle is involved in an accident and more specifically involves aninertia switch which will respond to a force of deceleration encounteredby the vehicle involved in an accident.

Inertia and acceleration switches heretofore known may be categorized bytheir response to a force applied in either a uniaxial direction of amulti-direction. These switches, however, are completely unsatisfactoryfor use in triggering a safety device when a vehicle is in an accident.That is, a switch of the character described must meet two basicrequirements:

a. It must respond to decelerations or accelerations in a horizontalplane for preset angular extent at each side of a direct forward line ofmotion, and

b. it must not respond to any force having a magnitude less than apredetermined adjustable amount for a duration less than a desiredperiod.

The prior art switches will not meet the first of the two basicrequirements mentioned above, because their response is not limited to aprescribed angular extent in one or more planes. Furthermore, the priorart switches will not meet the magnitude and time discriminatoryrequirements and also permit wide angle equal response over a wideoperating temperature range.

In accordance with the present invention an inertia switch assemblywhich meets both basic requirements is comprised of a casing in which isa pivotably mounted inertia switch having a cylindrical body containingswitch terminals and a movable conductive member which bridges theswitch terminals. The switch terminals themselves serve as pivots forthe cylindrical body which is free to turn in a plane so that the switchcan align itself axially with a line of deceleration in a prescribedangular pattern. The limits of free swing of the switch body may be setby abutments provided in the casing. A preferred form of the inertialswitch is a gas damped switch having a hollow piston with an orifice atone end with the piston being movable axially in a hollow cylindricalgas-filled body, opposed in its motion by a spring or other elasticmeans. Movement of the piston in response to applied forces ofacceleration or deceleration is gas damped. The piston carries aconductive plate or disk to bridge the switch terminals.

The pivotable mounting of the switch body is such that the switch bodywill align itself with the direction of applied force faster than thepiston in the switch body will respond to the applied force. Statedanother way, the pendulous response rate of the switch body is fasterthan the linear response of the gasdamped inertia element in the switchbody. The natural frequency and damping ratio of the air damped inertiaelement are adjusted to make the switch respond to any magnitude ofacceleration larger than a prescribed minimum limit, so as to obtaindiscrimination between a crash situation and a noncrash situation whenthe switch assembly is installed in a vehicle.

It is therefore, a principal object of the present invention to providean inertial switch assembly for triggering a safety device in a vehiclecollision.

It is another object of the present invention to provide inertial switchwhich will align itself with the direction of an applied force.

It is still another object of the present invention to provide aninertial switch which is pendulously mounted and wherein the pendulousresponse rate is faster than the response of the inertial switch.

These and other objects and many of the attendant advantages of thisinvention will readily be appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings in which:

FIG. 1 is a prespective view of an inertia switch assembly embodying theinvention;

FIG. 2 is another perspective view of the inertia switch assembly shownin an inverted position;

FIG. 3 is a top plane view of the inertia switch assembly with part ofthe casing broken away to show internal construction;

FIG. 4 is an enlarged central sectional view taken along line 4-4 ofFIG. 3;

FIG. 5 is a fragmentary cross sectional view on a reduced scale takenalong line 5-5 of FIG. 4; and

FIG. 6 is an exploded perspective view of parts of the switch assembly.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout, there is illustratedan inertia switch assembly generally designated as reference numeral 10having a flat cylindrical casing 12. The casing 12 has a cylindricalwall 14 and opposite circular end walls 16, 18. If desired the wall 16may be integral with the wall 14 and wall 18 may serve as a closureplate and seat on a shoulder 20 formed in the end wall 14. A mountingbracket plate 21 is secured to end wall 16 and has apertured tabs 23 formounting the assembly 10 in a vehicle. A pair of stationary metal cups22, 24 are set in respective holes 25, 26 centrally aligned with eachother in respective end walls l6, 18 but offset radially from the centeror central axis of the cylindrical casing 12. lnsulative disks 28, 30are set in the cups 22, 24 and have respectively secured thereto andextending therethrough metal pins 32, 34. If desired each combination ofdisk, cup and pin may comprise a fused ceramic to metal header forhermetically sealing the casing 12. These pins are axially aligned andserve as electrical terminals for a switch which is normally open(electrically) and also serve as pivots for the cylindrical switch 35.

The switch 35 as best shown in FIGS. 3-6 includes a tubular orcylindrical body 36 made of a plastic or of a metal such as aluminum.Set in holes 38 in opposite sides of body 36 are insulative trunnions 40provided with axial holes 42 which receive the pins 32, 34. Thetrunnions serve as bearing members permitting free swinging of switch 35in a plane perpendicular to the aligned axes of the pins 32 34 andparallel to the end walls 16, 18 ofthe casing 12.

When the casing 12 is axially vertical as shown in FIG. 3, the tabs 23will be vertical and may be secured by suitable screws to a fire wall orother appropriate surface S in a vehicle. The switch 35 will then befree swinging in a horizontal plane. Resilient abutment blocks 44 madeof felt, urathane foam or rubber are secured to the inside ofcylindrical wall 14 at points spaced apart. These blocks serve as stopmembers to limit the free swinging movement of the switch 35. Themounting of the assembly will be such that direction D represents theforward direction of movement of the vehicle carrying the assembly 10.The switch 35 is shown in FIG. 3 as axially oriented in direction D andis free to swing laterally to the right or left in angle A which isshown as approximately 120. In order to effect closure of an externalcircuit (not shown) connected to pins 32, 34 there is provided asinertia means comprising a movable switch ring 50. The switch ring is athin flat elec trically conductive metallic member mounted at one end 51of a mass or piston 52 which is cylindrical and is slidably disposed inan axial, cylindrical passage in the switch body 36 (FIGS. 4-6). Piston52 is hollow and receives a coil spring 56 which extends axially out ofthe open end 57 of the piston 52 and seats around a stud 58 formed onthe inner end of a plug 60. If desired the plug 60 may have an externalthread 61 adapted to mate in a threaded hole 62 at the distal end of thebody 36. The switch ring 50 is engaged on a shoulder 64 defined by aneck 66 at the proximal end 51 of the piston 52. On this neck is a coilspring 68 held in compression by the head 70 of a screw 72 and yieldablybearing on the switch ring 50. The shank of the screw 72 is engaged inthe internally threaded neck 66 of the piston 52. An axial hole 74extending entirely through the screw 72 communicates with the interiorof a chamber 75 in the piston 52. The hole 74 permits air flow betweenchamber 75 and a chamber 76 at the adjacent end of the body 36. Chamber76 is closed by a circular disk or plate 78 set in the end of the body36.

Referring to FIG. 4 it will be noted that the switch ring 50 is normallyspaced to the right of the aligned pins 32, 34 when the assembly isstationary and when it is moving in the forward direction D. If amechanical impulse due to collision or a sudden deceleration of theassembly 10 occurs, the body 36 will first respond by swinging freely toalign itself axially with the direction of applied impulse. Then thepiston 52 will respond by compressing the spring 56 and moving axiallyin body 36 until the switch ring 50 contacts both pins 32, 34 to closethe electric circuit in which the pins will be connected. The spring 68insures contact of the switch ring 50 with both pins in the event thepins 32, 34 are not axially aligned or the switch ring is not flat, etc.The response time of the piston 52 to the applied pulse is determined bya number of factors such as mass of the piston, stiffness of the spring56 and size of the hole 74 in the screw 72. The stiffness of spring 56may be adjusted most conveniently by substituting or selecting a springof desired length and stiffness. Similarly a piston of greater or lessermass may be selected, and/or a screw having an axial hole 74 of greateror lesser diameter may be selected. The largest measure of control ofthe switch assembly is exerted by the air damping (due to air trapped inthe chamber 75 in the piston 52) and this insures that the body 36 willalign itself first in the direction of the applied impulse before thepiston 52 moves to close the circuit terminals 32 34 via the conductiveswitch ring 50. I

It is possible that other types of inertia switch elements can beemployed in the switch body 36, such as those operating in a magneticfield or those having movable mercury contacts, etc. However, regardlessof the particular type of inertia switch employed it must meet the basicrequirement of response only to an impulse of a magnitude greater than apredetermined limit, and its response must be somewhat slower than theresponse time of the free swinging body 36.

The switch assembly 10 has particular utility in vehicles equipped withautomatic systems for inflating protective plastic cushions in the eventof an accident. The switch assembly may be used to trigger operation ofthe system. However the switch assembly is of general utility and may beused wherever an impulse responsive inertia switch is required torespond to an impulse in a prescribed angular pattern in a plane. Theprinciples of the invention may be applied to switch assemblies whereinthe inertia switch body 36 may be mounted by universal joint means toswing in a desired spherical angular vector pattern.

It should be understood that the foregoing relates to only a preferredembodiment of the invention, and that it is intended to cover allchanges and modifications of the example of the invention herein chosenfor the purposes of the disclosure, which do not constitute departuresfrom the spirit and scope of the invention.

The invention claimed is:

1. An inertia switch assembly comprising a support means subject to anapplied directional impulse;

an impulse responsive switch body pivotally carried by said supportmeans to swing freely thereon for self-orientation in the direction ofapplication of said impulse; and

impulse responsive inertia means in said switch body arranged to move insaid direction to close an external electric circuit and means wherebysaid inertia means respond slower to said impulse than said switch bodyso that said inertia means will close said external electric circuitonly after said body orients itself in said direction.

2. An inertia switch assembly as defined in claim 1, further comprisingstop means carried by said support means and disposed to limit swingingof said switch body to a prescribed angular pattern.

3. An inertia switch assembly as defined in claim 1, further comprisingpivot means pivotally mounting said body on said support means andarranged so that free swinging of said body is limited to at least oneplane.

4. An inertia switch assembly as defined in claim 3, wherein saidsupport means is a cylindrical casing mountable in an axially verticalos ition and includes ivot means dis osed axially vertrcal 0 limit freeswinging 0 said body to a orrzontal plane.

5. An inertia switch assembly as defined in claim 4, wherein said pivotmeans comprises axially aligned pins carried by said casing, said switchbody comprising a cylindrical member containing said inertia means; andtrunnions on said cylindrical member receiving said pins so that saidcylindrical member swings freely thereon.

6. An inertia switch assembly, as defined in claim 4, further includesstop means spaced apart circumferentially of and within said casing forlimiting angular movement of said switch body to a prescribed angularpattern.

7. An inertia switch assembly as defined in claim 5, wherein saidinertia means comprises a conductive element movably disposed insidesaid cylindrical member, said pins being electrically conductive andextending into said cylindrical member; and biasing means in saidcylindrical member normally holding said conductive element spaced fromsaid pins in such a way that said conductive element contacts said pinsto bridge the same mechanically and electrically in response to saidapplied impulse.

8. An inertia switch assembly as defined in claim 7, wherein saidinertia means further comprises a mass movable in response to saidimpulse only after said cylindrical member orients itself in saiddirection, said mass carrying said conductive element.

9. An inertia switch assembly as defined in claim 8, wherein said massis a gas-damped cylindrical piston, said cylindrical member having anaxial passage slidably supporting said piston; said biasing meanscomprising a spring engaged between said body and said piston foryieldably holding said conductive element spaced from said pins.

10. An inertia switch assembly as defined in claim 9, wherein saidpiston is hollow to define a first gas-containing chamber, said axialpassage in said cylindrical body defining a second gas-containingchamber, and means defining an aperture in said piston to providerestricted communication between said chambers for limited passage ofsaid gas therebetween, whereby movement of said piston in response tosaid impulse is gas-damped.

1. An inertia switch assembly comprising a support means subject to anapplied directional impulse; an impulse responsive switch body pivotallycarried by said support means to swing freely thereon forself-orientation in the direction of application of said impulse; andimpulse responsive inertia means in said switch body arranged to move insaid direction to close an external electric circuit and means wherebysaid inertia means respond slower to said impulse than said switch bodyso that said inertia means will close said external electric circuitonly after said body orients itself in said direction.
 2. An inertiaswitch assembly as defined in claim 1, further comprising stop meanscarried by said support means and disposed to limit swinging of saidswitch body to a prescribed angular pattern.
 3. An inertia switchassembly as defined in claim 1, further comprising pivot means pivotallymounting said body on said support means and arranged so that freeswinging of said body is limited to at least one plane.
 4. An inertiaswitch assembly as defined in claim 3, wherein said support means is acylindrical casing mountable in an axially vertical position, andincludes pivot means disposed axially vertical to limit free swinging ofsaid body to a horizontal plane.
 5. An inertia switch assembly asdefined in claim 4, wherein said pivot means comprises axially alignedpins carried by said casing, said switch body comprising a cylindricalmember containing said inertia means; and trunnions on said cylindricalmember receiving said pins so that said cylindrical member swings freelythereon.
 6. An inertia switch assembly, as defined in claim 4, furtherincludes stop means spaced apart circumferentially of and within saidcasing for limiting angular movement of said switch body to a prescribedangular pattern.
 7. An inertia switch assembly as defined in claim 5,wherein said inertia means comprises a conductive element movablydisposed inside said cylindrical member, said pins being electricallyconductive and extending into said cylindrical member; and biasing meansin said cylindrical member normally holding said conductive elementspaced from said pins in such a way that said conductive elementcontacts said pins to bridge the same mechanically and electrically inresponse to said applied impulse.
 8. An inertia switch assembly asdefined in claim 7, wherein said inertia means further comprises a massmovable in response to said impulse only after said cylindrical memberorients itself in said direction, said mass carrying said conductiveelement.
 9. An inertia switch assembly as defined in claim 8, whereinsaid mass is a gas-damped cylindrical piston, said cylindrical memberhaving an axial passage slidably supporting said piston; said biasingmeans comprising a spring engaged between said body and said piston foryieldably holding said conductive element spaced from said pins.
 10. Aninertia switch assembly as defined in claim 9, wherein said piston ishollow to define a first gas-containing chamber, said axial passage insaid cylindrical body defining a second gas-containing chamber, andmeans defining an aperture in said piston to provide restrictedcommunication between said chambers for limited passage of said gastherebetween, whereby movement of said piston in response to saidimpulse is gas-damped.